Abstract

Phosphorescent organic semiconductors normally show negligible magnetic field effects in electronic and optic responses. These phenomena have been generally attributed to strong spin-orbital coupling which can dominate internal spin-dephasing process as compared with applied magnetic field. This paper reports both positive and negative magnetocurrents from phosphorescent organic semiconductors through dissociation and charge-reaction channels when the intermolecular spin-orbital coupling is changed based on materials mixing. Our experimental results indicate that inter-molecular spin-orbital coupling is essentially responsible for the generation of magnetic field effects in phosphorescent organic semiconductors.

The research has been supported by U.S. NSF (ECCS-046645; OISE-0929566) and China NSF (50928302). The authors (C. F. O. Graeff and I. Hummelgen) would like to thank the support from CNPq (Brazil) and FAPESP (Brazil).